The company said late Wednesday that it had resolved the issue and Walmart.com is now operating normally. Walmart.com had intermittent problems with availability throughout the day as the discounter was trying to fix the problem.

"We apologize for any inconvenience to our customers," said Ravi Jariwala, a spokesman for Wal-Mart's online operations.

Earlier Wednesday, shoppers took to Twitter to cite ridiculously low prices like treadmills for $33.16 and Hewlett Packard LCD monitors for $8.85. Jariwala said that the company is notifying customers who ordered these items that their orders have been canceled and they'll be refunded in full. In addition, it will send customers a $10 e-gift card that can be used toward future purchases at its stores or on its website.

Heading into the crucial holiday shopping season, Wal-Mart has doubled the number of items it has on its website from last year to 5 million.

That's expected to help fuel 30% growth in online sales to $10 billion for its current fiscal year, which ends in late January. That's still just a sliver of the $486 billion in annual sales Wal-Mart did last year.